Post-review fixes + some locking cleanup.

storage/maria/ma_loghandler.c:
  translog_lock() made safe (non-mutex-protected operation is atomic now).
  Fixed translog_destroy() because it will not work to be
    called several times.

storage/maria/ma_loghandler.c

@@ -2362,7 +2362,7 @@ static my_bool translog_page_validator(uchar *page_addr, uchar* data_ptr)
 
 my_bool translog_lock()
 {
-  struct st_translog_buffer *current_buffer;
+  uint8 current_buffer;
   DBUG_ENTER("translog_lock");
 
   /*
@@ -2371,12 +2371,16 @@ my_bool translog_lock()
   */
   for (;;)
   {
-    current_buffer= log_descriptor.bc.buffer;
-    if (translog_buffer_lock(current_buffer))
+    /*
+      log_descriptor.bc.buffer_no is only one byte so its reading is
+      an atomic operation
+    */
+    current_buffer= log_descriptor.bc.buffer_no;
+    if (translog_buffer_lock(log_descriptor.buffers + current_buffer))
       DBUG_RETURN(1);
-    if (log_descriptor.bc.buffer == current_buffer)
+    if (log_descriptor.bc.buffer_no == current_buffer)
       break;
-    translog_buffer_unlock(current_buffer);
+    translog_buffer_unlock(log_descriptor.buffers + current_buffer);
   }
   DBUG_RETURN(0);
 }
@@ -3348,10 +3352,12 @@ void translog_destroy()
   uint i;
   DBUG_ENTER("translog_destroy");
 
-  if (translog_inited)
-  {
+  DBUG_ASSERT(translog_inited);
+  translog_lock();
+  translog_inited= 0;
   if (log_descriptor.bc.buffer->file != -1)
     translog_finish_page(&log_descriptor.horizon, &log_descriptor.bc);
+  translog_unlock();
 
   for (i= 0; i < TRANSLOG_BUFFERS_NO; i++)
   {
@@ -3375,8 +3381,6 @@ void translog_destroy()
   my_close(log_descriptor.directory_fd, MYF(MY_WME));
   my_atomic_rwlock_destroy(&LOCK_id_to_share);
   my_free((uchar*)(id_to_share + 1), MYF(MY_ALLOW_ZERO_PTR));
-    translog_inited= 0;
-  }
   DBUG_VOID_RETURN;
 }
 
@@ -3803,6 +3807,7 @@ static my_bool translog_advance_pointer(uint pages, uint16 last_page_data)
                                log_descriptor.bc.current_page_fill),
                        pages, (uint) log_descriptor.page_overhead,
                        (uint) last_page_data));
+  translog_lock_assert_owner();
 
   for (;;)
   {